Short range wireless systems utilizing radio frequency (RF) integrated circuits use time division multiplexing for transmitting and receiving signals. The transmitted signals and the received signals use the same frequency band. However, the transmitting (Tx) and receiving (Rx) paths often use differential signaling after a certain stage for increasing performance. The short range wireless systems use a single antenna for both transmission (Tx) and reception (Rx) of signals by utilizing a transmit and receive (T/R) switch. The transmit and receive (T/R) switch toggles the antenna between transmission (Tx) and reception (Rx). The transmit and receive (T/R) switch needs high linearity at high signal swing. A block diagram of a conventional radio frequency (RF) front-end with a transmit and receive (T/R) switch is shown in FIG. 1. For each communication band, the transmit and receive (T/R) switch couples an antenna and a balun either to a low noise amplifier (LNA) of a receiver or to a power amplifier (PA) of a transmitter.
Differential implementation of radio frequency front-ends and analog circuit sections is a critical need, particularly in system-on-a-chip (SOC) scenarios which are characterized by noisy environment and different package requirements. Input lines of the receiver low noise amplifier (LNA) and output lines of the transmitter power amplifier (PA) can either be combined on-chip with common pins brought out for antenna connection or separate pins brought out and combined externally for further connection to an antenna. Conventionally, both these methods are complex and require many internal or external components. These methods often involve having the transmit and receive (T/R) switch disconnect a transmitter (Tx) during a receiver (Rx) operation and vice versa. The transmit and receive (T/R) switch losses directly affect the receiver (Rx) sensitivity and transmitter (Tx) output power delivery. Transmit and receive (T/R) operation can also be implemented using on-chip transformer component. However the on-chip radio frequency (RF) transformer component is not available in many foundries. Furthermore, the on-chip radio frequency (RF) transformer component is not well characterized and induces several signal losses upon implementation.
It would be desirable if the entire radio frequency (RF) front-end could be integrated with the baseband and radio or portions eliminated and the remainder be fully integrated for short range wireless, cellular and other communications.
Hence there is a long felt but unresolved need for a compact radio frequency (RF) front-end with reduced chip area (real estate), reduced energy dissipation, reduced signal loss, reduced switching loss, and reduced cost of manufacture while providing a variety of circuit and system products.